One-Pot Direct Conversion of 2,3-Epoxy Alcohols into Enantiomerically Pure 4-Hydroxy-4,5-dihydroisoxazole 2-Oxides
摘要:
[GRAPHICS]A new methodology for the one-pot direct conversion of 2,3-epoxy alcohols into enantiomerically pure 4-hydroxy-4,5-dihydroisoxazole P-oxides 1 has been found. The reaction works at room temperature and can be run at the 5-10 g scale. The mixture of 4,5-cis and 4,5-trans isomers obtained can be separated as such or as the bis-TDS ethers, A preliminary example of reductive cleavage of 1 to the corresponding amino polyol is also reported.
Mapping the substrate selectivity of new hydrolases using colorimetric screening: lipases from Bacillus thermocatenulatus and Ophiostoma piliferum, esterases from Pseudomonas fluorescens and Streptomyces diastatochromogenes
作者:Andrew Man Fai Liu、Neil A Somers、Romas J Kazlauskas、Terry S Brush、Frank Zocher、Markus M Enzelberger、Uwe T Bornscheuer、Geoff P Horsman、Alessandra Mezzetti、Claudia Schmidt-Dannert、Rolf D Schmid
DOI:10.1016/s0957-4166(01)00072-6
日期:2001.3
screened a general library of 29 substrates and a chiral library of 23 pairs of enantiomers. All four hydrolases catalysed the hydrolysis of unnatural substrates, but the two lipases accepted a broader range of substrates than the two esterases. As expected, the two lipases favoured more hydrophobic substrates, while the two esterases showed a preference for smaller substrates. Several moderately enantioselective
ether-oxygen to the stereogenic quaternary carbon center of the oxirane ring had a profound influence on the enantioselectivity, and several oxiranes were resolved with good to excellent selectivities. The enantiomerically enriched epoxides and vicinal diols thus obtained contain a useful “synthetic handle” in their side chain, which allows their use as buildingblocks in asymmetric synthesis.
The present invention discloses compounds of Formula (I), or pharmaceutically acceptable salts, esters, or prodrugs thereof: which inhibit Human Respiratory Syncytial Virus (HRSV) or Human Metapneumovirus (HMPV) inhibitors. The present invention further relates to pharmaceutical compositions comprising the aforementioned compounds for administration to a subject suffering from HRSV or HMPV infection. The invention also relates to methods of treating an HRSV or HMPV infection in a subject by administering a pharmaceutical composition comprising the compounds of the present invention.
Chemo- and stereoselectivity in the ring-openingreaction of epoxides with a reagent prepared from allylmagnesium halide and chlorotitanium triphenoxide is described. It has been proven that the allylating reagent can also be used for the reaction of epoxides bearing a tert-butyl ester, amide, or acetal moiety, and that the epoxide cleavage regioselectively takes place at the more substituted carbon
(S)-(−)- and (R)-(+)-Frontalin were synthesized, respectively, in high enantiomer excess from β-methallyl alcohol (2) by three-step procedure; (i) asymmetric epoxidation of 2, (ii) the epoxide opening with homoallylmagnesium bromide, and (iii) Pd(II)-catalyzed intramolecular acetalization.